Hydraulic and mechanical noise isolation for improved formation testing

ABSTRACT

An apparatus and method for isolating a downhole tool section from hydraulic and mechanical noise. Anchoring grippers are used in conjunction with a fluid diverter valve to anchor the tool section to a borehole wall and divert fluid flowing in the drill string away from sensitive test equipment during formation testing.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part patent application of co-pendingU.S. patent application Ser. No. 09/703,645 filed on Nov. 1, 2000 andtitled “Modified Formation Testing Apparatus with Borehole Grippers andMethod of Formation Testing”, the application being hereby fullyincorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to the testing of underground formationsor reservoirs. More particularly, this invention relates to a method andapparatus for isolating a downhole test tool from vibration and noisedue to heave and/or drilling fluid circulation during formation testing.

[0004] 2. Description of the Related Art

[0005] While drilling a well for commercial development of hydrocarbonreserves, several subterranean reservoirs and formations areencountered. In order to discover information about the formations, suchas whether the reservoirs contain hydrocarbons, logging devices havebeen incorporated into drill strings to evaluate several characteristicsof these reservoirs. Measurement-while-drilling systems (hereinafterMWD) have been developed that contain resistivity, nuclear and otherlogging devices which can constantly monitor formation and reservoircharacteristics during drilling of well boreholes. The MWD systems cangenerate data that include information about the presence ofhydrocarbon, saturation levels, and formation porosity. Telemetrysystems have been developed for use with the MWD systems to transmit thedata to the surface. A common telemetry method uses a mud-pulsed system,an example of which is found in U.S. Pat. No. 4,733,233 incorporatedherein by reference. MWD systems provide real time analysis of thesubterranean reservoirs.

[0006] Commercial development of hydrocarbon fields requires significantamounts of capital. Before field development begins, operators desire tohave as much data as possible in order to evaluate the reservoir forcommercial viability. Despite the advances in data acquisition duringdrilling using the MWD systems, it is often necessary to conduct furthertesting of the hydrocarbon reservoirs in order to obtain additionaldata. Therefore, after the well has been drilled, the hydrocarbon zonesare often tested by other test equipment.

[0007] One type of post-drilling test involves producing fluid from thereservoir, collecting samples, shutting-in the well and allowing thepressure to build-up to a static level. This sequence may be repeatedseveral times for different reservoirs within a given borehole. Thistype of test is known as a “Pressure Build-up Test.” One of theimportant aspects of the data collected during such a test is thepressure build-up information gathered after drawing the pressure down.From this data, information can be derived as to permeability and sizeof the reservoir. Further, actual samples of the reservoir fluid areobtained and tested to gather Pressure-Volume-Temperature data relevantto hydrocarbon distribution in the reservoir.

[0008] The drill string is often retrieved from the well borehole toperform these tests in an operation known as tripping. A different tooldesigned for the testing is then run into the well borehole. A wirelineis then used to lower a test tool into the well borehole. The test toolsometimes utilizes packers for isolating the reservoir. Alternatively, awire line can be lowered from the surface, into a landing receptaclelocated within a drill string test tool, establishing electrical signalcommunication between the surface and the test assembly. Regardless ofthe type of test tool and type of communication system used, the amountof time and money required for retrieving the drill string and/orrunning a second test tool into the borehole is significant. Further, ifthe borehole is highly deviated, a wire line tool is difficult to use toperform the testing.

[0009] Various MWD tools have been developed to allow for the pressuretesting and fluid sampling of potential hydrocarbon reservoirs as soonas the borehole has been drilled into the reservoir, without removal ofthe drill string. These MWD tools also reduce the risks associated withpressure kick, because the drilling fluid pressure can be monitored andmaintained better when tripping is avoided.

[0010] The typical MWD tool, however, suffers in that vibrations causedby flowing drilling fluid, mud pumps, drilling motors and surfaceequipment are transmitted to the test device through the drill string oreven directly in the case of flowing drilling fluid. These vibrationsoften adversely affect test results, because the downholeinstrumentation can be too sensitive to operate effectively inmechanically noisy environment.

[0011] Another problem is associated with vertical movement known asheave encountered when drilling in an offshore environment. Heavemovement can cause pressure leaks where probe sealing pads and packersengage the borehole wall to form a seal. Heave movement can also resultin excessive wear on soft materials used for sealing against theborehole wall. Although such heave is normally associated with offshoredrilling, any unwanted vertical movement while a seal is engaged withthe borehole wall can damage the seal material or cause unwanted leaks.Therefore, the use of the term heave is not meant to limit theusefulness of the present invention to offshore drilling environments.The present invention addresses the need to have a MWD tool thatprovides protection to sensitive test devices and protects soft sealingmaterials from unwanted movements that cause excessive wear on suchmaterials.

SUMMARY OF THE INVENTION

[0012] A formation testing method and a test apparatus are disclosed.The test apparatus is mounted on a work string for use in a wellborehole filled with fluid. It can be a work string designed fordrilling, re-entry work, or workover applications in either on oroffshore drilling operations. The work string is preferably adapted forconveying into highly deviated holes, horizontally, or even uphill. Thework string preferably includes a Measurement While Drilling (MWD)system and a drill bit, or other operative elements.

[0013] One aspect of the present invention provides a downhole tool foracquiring a parameter of interest. The tool being conveyed into a wellborehole on a work string having a rotatable bit at a distal endthereof. The tool includes an independently extendable gripper elementdisposed on the work string, wherein the extendable gripper elementforcibly engages the borehole wall to anchor at least a portion of thedrill string radially, axially and circumferentially while the boreholewall is engaged by the gripper element. A diverter valve is coupled tothe drill string either above or below the gripper element to divertdrilling fluid into the annulus. A test device is coupled to the workstring for determining the parameter of interest.

[0014] In another aspect of the present invention a system for acquiringa downhole parameter of interest while drilling a borehole through aformation includes a drill string having a rotatable bit at a distal endthereof. An independently extendable gripper element is disposed on thedrill string to forcibly engage the borehole wall to anchor at least aportion of the drill string radially, axially and circumferentiallywhile the borehole wall is engaged by the extendable gripper element. Adiverter valve is preferably coupled to the drill string above thegrippers to divert drilling fluid into the annulus. A test device iscoupled to the drill string portion and includes a sensor for measuringa desired downhole characteristic and for providing an output signalrepresentative of the measured characteristic. A processor receives andprocesses the output signal, the processed signal being indicative ofthe parameter of interest.

[0015] A method of isolating a downhole test device from noise is alsoprovided. The method includes conveying a drill string into a wellborehole, the drill string having a rotatable bit at a distal endthereof and an inner bore for conveying drilling fluid from a surfacelocation to the drill bit. A drill string portion is anchored to theborehole wall using an independently extendable gripper element. Themethod includes diverting drilling fluid above the anchored drill stringportion using a diverter valve, and obtaining a desired characteristicusing a sensor disposed on the anchored drill string portion.

[0016] The gripper elements may be incorporated on the work string or ona non-rotating sleeve. The grippers are extendable and are used toengage the borehole wall. Once the borehole wall is engaged, thegrippers anchor the work string or non-rotating sleeve such that thework string or non-rotating sleeve remains substantially motionlessduring a test, i.e. to prevent movement radially, axially andcircumferentially while the borehole wall is engaged by the gripperelement. The advantage of anchoring the tool is increased useful life ofsoft components such as pad members and packers and to reduce noisecaused by vibrations associated with the work string that adverselyaffect sensitive test equipment and test data.

[0017] An advantage of the present invention includes use of thepressure and resistivity sensors with the MWD system, to allow for realtime data transmission of those measurements. Another advantage is thatthe present invention allows obtaining static pressures, pressurebuild-ups, and pressure draw-downs with the work string such as a drillstring in place and in an extremely quiet environment free of vibrationand movement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a detailed understanding of the present invention, referencesshould be made to the following detailed description of the preferredembodiment, taken in conjunction with the accompanying drawings, inwhich like elements have been given like numerals and wherein:

[0019] FIGS. 1A-B are elevation views of the apparatus of the presentinvention as it would be used with a floating drilling rig;

[0020]FIG. 2 is a functional block diagram of surface and downholeelements of the present invention.

[0021]FIG. 3 is a cross section of a downhole tool portion according toan embodiment of the present invention showing a diverter valve;

[0022]FIG. 4A is a cross section of a downhole tool portion according toan embodiment of the present invention showing a gripper element;

[0023] FIGS. 4B-C show alternative embodiments of the gripper element ofFIG. 4A;

[0024] FIGS. 5A-G show various textures for a gripper surface forincreasing friction between the gripper and borehole wall;

[0025]FIG. 6 is a perspective view of an embodiment of the presentinvention showing gripper elements integral to stabilizers and anextendible sealing pad element integral to a stabilizer; and

[0026]FIG. 7 is a perspective view of an embodiment of the presentinvention that includes integrated stabilizers and grippers, packers andan extendable sealing pad element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Referring to FIG. 1, a typical drilling rig 102 with a wellborehole 104 extending therefrom is illustrated, as is well understoodby those of ordinary skill in the art. The drilling rig 102 has a workstring 106, which in the embodiment shown is a drill string. The workstring 106 has attached thereto a drill bit 108 for drilling the wellborehole 104. The present invention is also useful in other types ofwork strings, and it is useful with jointed tubing as well as coiledtubing or other small diameter work string such as snubbing pipe.Therefore, the term “work string” as used herein includes each of theseseveral types of work string. FIG. 1 depicts the drilling rig 102positioned on a drill ship S with a riser extending from the drillingship S to the sea floor F. If applicable, the work string 106 can have adownhole drill motor 110 for rotating the drill bit 108. The drill bitmight be rotated using a surface motor rotating a drill pipe. Fixed ribsor stabilizers 112 are positioned at the lower portion of the workstring 106 to stabilize the string as drilling progresses.

[0028] Incorporated in the drill string 106 above the drill bit 108 is atool 116. The tool 116 includes a test device 114 for testing formationfluid or other properties of a traversed reservoir 118. The tool 116 isa portion of the overall work string 106 and includes one or moregripper elements 120 a and 120 b to anchor a portion 106 a of the workstring 106. In a preferred embodiment at least one gripper element 120 ais located above the test device 114, and a diverter valve 122 isdisposed above or uphole of the upper gripper element 120 a. As will bedescribed in more detail later, one embodiment includes a diverter valvebelow an upper gripper element 120 a to operate a force multiplier.

[0029] The gripper elements 120 a/120 b are extendable to engage theborehole wall 104. Once engaged the gripper elements are forcefullypressed against the wall to anchor the portion 106 a of the work string106, which might contain sensitive test devices 114. Such anchoringisolates the test device 114 from unwanted vibrational and othermechanical noise while formation tests are performed. The isolation isparticularly desirable when the test device includes sensitive testelements such as a nuclear logging instrument. Another desirable aspectof anchoring the test portion is protecting from excessive wear softmaterials such as seals used to isolate an area of the borehole wall.The gripper elements operate to anchor the drill string portionradially, axially and circumferentially while tests are performed. Asused herein, anchoring means to forcefully couple a device or workstring portion to the borehole wall to restrain the anchored portionfrom movement in axial, radial and/or circumferential directions. Suchanchoring prevents vertical motion from destroying the seals andprevents pressure leaks by ensuring the sealing pads stay in place.

[0030] The tool 116 further includes a sensor system 124 thatincorporates various sensors 126 useful for in situ formation testing.Examples of such sensors include pressure sensors, flow sensors, nuclearmagnetic resonance (“NMR”) sensors, resistivity sensors, porositysensors, etc . . . . The tool can also include devices for sampling andtesting formation fluid such as a sampling probe and/or packer. The toolcan be incorporated into a drill stem tester, which is a large volumetest device. The particular sensor and test device used is chosen basedon the desired test. The present invention is useful in any such testusing any such sensor where it is desirable to isolate the test devicefrom mechanical and/or hydraulic noise.

[0031] As depicted in FIG. 2, the invention includes use of a controlsystem 200 for controlling the various valves and pumps, and forreceiving the output of the sensor system 124. The control system 200 iscapable of processing the sensor information with a downholemicroprocessor/controller 204, and delivering the data to acommunications interface 206 so that the processed data can then betelemetered to the surface using conventional technology. It should benoted that various forms of transmission energy could be used such asmud pulse, acoustical, optical, or electromagnetic. The communicationsinterface 206 can be powered by a downhole electrical power source 208.The power source 208 also powers the sensor system 124, themicroprocessor/controller 204, and various valves and pumps.

[0032] Communication between downhole and surface equipment of the Earthcan be effected via the work string 106 in the form of acoustic energy,pressure pulses through annular fluids or other methods well known inthe art. In most cases, the transmitted information will be received atthe surface via a 2-way communication interface 210. The data thusreceived will be delivered to a surface computer 212 for interpretationand display.

[0033] Command signals may be sent down the fluid column by thecommunications interface 210 to be received by the downholecommunications interface 206. The signals so received are delivered tothe downhole microprocessor/controller 204. The controller 204 will thensignal the appropriate valves and pumps for operation as desired.

[0034] A bi-directional communication system as known in the art can beused as the interface 206. The purpose of the two-way communicationsystem or bi-directional data link being to receive data from thedownhole tool and to be able to control the downhole tool from surfaceby sending messages or commands. In one embodiment the only command isto initiate testing and the downhole controller conducts a desired testautonomously thereafter.

[0035] Data measured from the downhole tool 116 is preferablytransmitted to the surface in order to utilize the measured data forreal-time decisions and monitoring the drilling process. The datatypically relate to measurements that are obtained from the subsurfaceformation, such as formation pressure information, information aboutoptical properties or resistivity of the fluid, annulus pressure,pressure build-up or draw-down data, etc. The tool preferably transmitsinformation that used to control the tool during its operation. Forinstance, information about pressure inside packers versus pressure inthe annulus might be monitored to determine seal quality, informationabout fluid properties from the optical fluid analyzer or theresistivity sensor might be used to monitor when a sufficiently cleanfluid is being produced from the formation, or status informationpertaining to completion of operational steps might be monitored so thatthe surface operator, if required, can determine when to activate thenext operational step. One example could be that a code is pulsed tosurface when an operation is completed, for instance, activation ofpacker elements or extending a pad or other device to engage contactwith the borehole wall. This data, or code, is then used by the operatorto control the operation of the tool. Additionally, the downhole toolcould transmit to the surface information concerning the status of itshealth and information pertaining to the quality of the measurements.

[0036]FIG. 3 is a cross section of a downhole tool portion according toan embodiment of the present invention showing a diverter valveaccording to the present invention. Shown is a valve 300 disposed in adrill string portion 302. The valve 300 includes a hydraulic piston 304that can be controlled from the surface or by a downhole controller 204.The hydraulic piston 304 operates to control a sealing device 306 in amain channel 308 of the drill string 106. The device 306 is preferably aplunger seal that seats in a beveled interior shoulder 310 of the drillstring portion 302. When seated in the shoulder 310, the plunger 306operates to interrupt fluid flow through the main channel 308.

[0037] The valve 300 further includes one or more flow valves 312 fordiverting the fluid flowing in the main channel to the borehole annulus.This allows continued fluid flow above or uphole of the seal 306 tooperate hydraulic components and downhole motors. When the main channelis sealed and the flow valves 312 are open, then any component downholeof the seal 306 is substantially isolated from hydraulic noise generatedby fluid flow while allowing continued flow above the seal 306.

[0038] In one embodiment the valve is positioned above a packer 128 toisolate the test device or sensor system 124 from pressure variationsand hydraulic noise in the annulus between the tool and borehole wallwhile diverter valve is diverting fluid. In one embodiment the valve isplaced above an upper gripper 120 a as shown in FIG. 1. In anotherembodiment not separately shown, the valve 300 is placed below a gripperto enable use of high pressure fluid in the main channel 308 inproviding pressure for the gripper.

[0039]FIG. 4 is a cross section of a downhole tool portion according toan embodiment of the present invention showing a gripper element 400.The gripper element 400 is preferably disposed on a portion 402 of thedrill string 106. The gripper element operates to forcefully engage theborehole wall to anchor at least the drill string portion 402 frommovement axially, circumferentially and radially to isolate the portionfrom mechanical vibrations associated with drilling operations and fluidflow. The force required for such anchoring is dependent on variousfactors, namely drill string weight, weight on bit, weight of anchoredportion, formation rock properties at the gripper location, etc . . . .Those skilled in the art with the benefit of this disclosure candetermine the necessary force to provide such anchoring without causingserious damage to the borehole wall at the anchoring location.

[0040] The gripper element 400 includes a housing 404 and one or morehigh-force pistons 406. One or more gripper pads 408 are positioned onthe pistons 406 so that the pistons 406 extend to forcefully press thepad 408 against the borehole wall 104. The pad 408 will typically pressthrough mudcake build-up on the borehole wall to anchor against theunderlying formation rock.

[0041] Anchoring force should be understood to be greater than the forcerequired to merely provide back-up to an extendable probe used to sampleformation fluid. The gripper, however, could be positioned to engage theborehole wall at the same depth as a sampling probe without damaging theprobe. For example, two gripper elements can be angularly positioned+/−90 degrees from an extendable probe to provide anchoring according tothe present invention as well as providing back-up force for thesampling probe without damaging the probe.

[0042] Various embodiments of the gripper element 400 can be used toprovide effective anchoring. The embodiment of FIG. 4A shows a singleelongated pad 408 extended by several individual pistons 406. The pad408 is tapered at its ends 408 a and 408 b to facilitate retracting thegripper pad 408. A cross section of just the pad portion 408 is shown inFIG. 5A to show the feature of tapered ends 500 a and 500 b on a padelement 500 along with variations of a textured surface 502. Since thepad 408/500 will most likely press through mudcake and possibly eveninto rock, the tapered ends help ensure that the gripper does not becomestuck or wedged into the formation. Although not apparent in the sideview provided here, the surface 502 gripper pad 500 is preferablyprovided with a curvature complementary to borehole wall for betterengagement therewith. Furthermore, the pad 500 further includes atextured surface to provide higher friction force between the pad andborehole wall.

[0043] In one embodiment the pad 408 is a tapered pad and generallycircular with a shallow conical shape. The pad is pressed into themudcake for gripping the borehole wall, and the conical shape enhancesthe ability to disengage the mudcake after a test. If the pad becomesstuck due to pressure differential or other cause, a movement of thedrill string will help disengage the pad.

[0044] FIGS. 5B-G show various textures for a gripper surface 502 forincreasing friction between the gripper and borehole wall. Exemplary yetnon-limiting textured surfaces shown in FIGS. 5B-G can be either raisedor indented patterns in the surface 502 of the pad 500. The surfacepattern can be diamond 504, raised points 506, ridges (or grooves) 508,dimples 510, cross-hatch 512, and/or circular 514 patterns.

[0045] Referring still to FIG. 4A, the embodiment shown includes a fixedpad or housing portion 410 that engaged the borehole wall opposite ofthe gripper pad 408. The gripper pad 408 and both ends 408 a/408 bextend outwardly from the housing 404. FIG. 4B shows an embodimenthaving a flexible arm or member 412 attaching one end of the gripper pad408 to the housing 404. FIG. 4C shows another embodiment having apivoting member 414 attached to a pivot point 416 on the housing 404 andto a pivot point 418 on the gripper pad 408. Each of these alternativeembodiments provides the ability to ensure the gripper element does notbecome stuck. Multiple grippers can also be disposed about thecircumference of the tool housing to allow the tool to remaincentralized in the borehole.

[0046] The gripper 400 can be disposed on the drill string 106 eitherabove or below the diverter valve 300. Those skilled in the art with thebenefit of this disclosure can easily determine how to best operate thegripper for the particular design chosen. For example, a gripper mountedbelow the diverter valve can be hydraulically operated using highpressure fluid in the interior channel of the tool by engaging thegripper before operating the diverter valve. Alternatively, the divertervalve can be fitted with a valve in the seal 306 to direct some fluidabove the seal to the gripper pistons below the seal while stillinhibiting fluid flow through the interior channel. A fluid forcemultiplier, which is known, can be used to provide additional force toeffect anchoring. It is also contemplated to use a pump, either above orbelow the diverter valve to pump high pressure fluid directly to thegripper pistons.

[0047] FIGS. 6-7, taken with FIGS. 1-5G show preferred toolconfigurations according to the present invention. FIG. 6 shows a toolsection 600 of a drill string 602 including a two-way communicationsystem 604 and power supply 606 disposed at its upper end. Thecommunication system 604 may comprise any number of well-knowncomponents suitable for the particular application and can be asdescribed above and shown in FIG. 2 at 206. A diverter valve 608 isdisposed on the tool section 600, and is preferably disposed below thepower supply 606 to allow continued circulation of mud for operate thepower supply while drilling is stopped for sampling and testing of aformation. The diverter valve 608 can be a valve substantially asdescribed above and shown in FIG. 3 at 300. Shown disposed below thediverter valve 608 is an optional sample chamber section 610. Gripperelements 612 are mounted on the tool section 600 below the divertervalve 608 and sample chamber section 610. The grippers 612 areessentially as described above and shown in FIG. 4A at 400. The grippersare selectively and preferably independently extendable with respect toan extendable probe 614 and can engage the wall of a borehole to anchorthe tool section 600 as described above. In the embodiment of FIG. 6,the grippers 612 might be integrated into one or more stabilizers 616,which operate to centralize the tool section 600 during drilling. Theextension requirement for the anchoring grippers 612 are minimized inthis embodiment, which creates a stronger and more stable anchoringsystem.

[0048] A pump 618 and at least one measurement sensor 620 such as apressure sensor are disposed in the tool section 600 for taking andmeasuring samples of formation fluid. A pad sealing element 622 isdisposed on the extendable probe 614, and a port 624 provides fluidcommunication to the pump 618 and pressure sensor 620. This embodimentfurther shows that the extendable probe 614 can be mounted on astabilizer 616 to reduce travel length for extending the probe 614.

[0049] During drilling operations, drilling would be momentarily stoppedfor testing a formation. A command to open the diverter valve 608 may beissued from a surface location or from the controller 204 disposed inthe tool section 600. The diverter valve 608 then opens in response tothe command to allow continued mud circulation through the drill string602 for operating the power supply 606. The grippers 612 are thenextended to engage the borehole wall to anchor the tool section. Oncethe tool section 600 is anchored in place the probe 614 is extended toseal a portion of borehole and is isolated from hydraulic and mechanicalvibrations and movement by use of the grippers 612 and diverter valve608.

[0050] Once the pad 622 is in sealing contact with the borehole wall,the pump is activated to reduce the pressure at the port 624. When thepressure is reduced at the port 624 formation fluid enters the port. Ifsamples are desired, the fluid is directed by internal valves to thesample chamber section 610. Measurements of fluid characteristics, suchas formation pressure, are taken with the sensor 620. The communicationsystem 604 is then used to transmit data representative of the sensedcharacteristic to the surface. The data may also be preprocesseddownhole by the downhole processor 204 of FIG. 2 disposed in the toolsection prior to transmitting the data to the surface.

[0051]FIG. 7 shows another embodiment of a tool section 700 according tothe present invention in a typical drill string 702. The tool section700 has a two-way communication system 704 and power supply 706 disposedat its upper end. The communication system 704 and the power supply 706may be comprised of any well-known components suitable for theparticular application and are substantially as described above andshown in FIGS. 2 and 6. A diverter valve 708 is disposed on the toolsection 700, and in systems using a mud turbine power supply istypically disposed below the power supply 706 to allow continuedoperation of the power supply while drilling is stopped for sampling andtesting of a formation. The diverter valve 708 is substantially asdescribed above and shown in FIGS. 3 and 6. Shown disposed below thediverter valve 708 is an optional sample chamber section 710.Stabilizers 716 with integrated grippers 712 are mounted on the toolsection 700 below the diverter valve 708 and sample chamber section 710.The grippers 712 and stabilizers 716 are essentially as described aboveand shown in FIGS. 4 and 6. The grippers 712 are selectively extendableand can engage a borehole to anchor the tool section 700. The lengths ofthe anchoring grippers 712 are thus minimized creating a stronger andmore stable anchoring system.

[0052] A pump 718 and at least one measurement sensor 720 such as apressure sensor are disposed in the tool section 700. The pump 718 andpressure sensor 720 are as described above and shown if FIG. 6. Upperand lower packers 726 and 728 are disposed on the tool section above andbelow a pad sealing element 714 mounted on an extendable probe 722. Thepackers 726 and 728 may be mud-inflatable packers as described above andare used to seal a portion of annulus around the pad sealing element 714from the rest of the annulus. The extendable probe 722 is operativelyassociated with the pump 718 and pressure sensor 720. The probe 722 isselectively extendable as described above in FIG. 6 and extends the padsealing element 714 to engage a borehole wall to seal a portion of thewall between the upper and lower packers 726 and 728. A port 724 locatedon the end of the pad sealing element 714 is in fluid communication withthe pump 718 and measurement sensor 720. Another port (not shownseparately) positioned on the tool section 700 between the packers 726and 728 may be used in conjunction with the pump 718 to reduce thepressure between the packers to enhance sealing at the probe seal 724.This can be done by pumping the mud trapped between the packers 726 and728 to the annulus above the upper packer 726. With pressure reducedbetween the packers below the pressure at the port a pressuredifferential is created between the port and the annulus between thepackers thereby ensuring that any leakage at the port is formation fluidleakage from the port into the annulus rather than mud from the annulusleaking into the port. Another set of stabilizers 716 and grippers 712may be positioned downhole of the lower packer 728 to provide added toolstabilization and anchoring during tests. A typical BHA including adrill bit (not shown) well known in the art, would be disposed on thedrill string 702 downhole of the depicted tool section 700. Operation ofthe embodiment of FIG. 7 is substantially similar to that of FIG. 6.

[0053] There could be any number of variations to the above-describedembodiments that do not require additional illustration. For example,alternate embodiments could be the embodiments of FIGS. 6-7 whereinseparate grippers and stabilizers are used, or wherein grippers are usedwithout stabilizers. An another useful embodiment, the tool section 600or 700 us integrated into a non-rotating sleeve to allow continuedmotion of the drill string while anchoring the sensitive test section.Those skilled in the art would understand without further illustrationthat the sleeve could include a spring and bearing to allow progressionof the drill bit while the gripper element anchors the nonrotatingsleeve. In such an embodiment the test device can be adapted todetermine a formation parameter of interest while the drill bit progressthrough the formation

[0054] The foregoing description is directed to particular embodimentsof the present invention for the purpose of illustration andexplanation. It will be apparent, however, to one skilled in the artthat many modifications and changes to the embodiment set forth aboveare possible without departing from the scope of the invention. It isintended that the following claims be interpreted to embrace all suchmodifications and changes.

We claim:
 1. A downhole tool for acquiring a parameter of interest, thetool being conveyed into a well borehole on a drill string having arotatable bit at a distal end thereof, the tool comprising: a) anextendable gripper element disposed on the drill string, wherein theextendable gripper element forcibly engages the borehole wall to anchorat least a portion of the drill string radially, axially andcircumferentially while the borehole wall is engaged by the extendablegripper element; b) a diverter valve coupled to the drill string todivert drilling fluid into the annulus; and c) a test device coupled tothe drill string portion for determining the parameter of interest. 2.The tool of claim 1, wherein the extendable gripper element includes atextured pad mounted on the gripper element to increase frictional forcebetween the borehole wall and the gripper element.
 3. The tool of claim2, wherein the pad is a single pad.
 4. The tool of claim 2, wherein thepad is a plurality of pads.
 5. The tool of claim 2, wherein the pad is asingle elongated pad attached to a housing using at least one of i) aflexible member coupling the pad to the housing and ii) a membercoupling the pad to the housing at a pivot point.
 6. The tool of claim2, wherein the pad has a tapered end.
 7. The tool of claim 1, whereinthe extendable gripper element further includes one or more pistons anda pad, the one or more pistons operable to extend the pad to engage theborehole wall.
 8. The tool of claim 7, wherein the pad is has a conicalshape pressed into mudcake when the extendable gripper element engagesthe borehole wall.
 9. The tool of claim 2, wherein the textured padincludes a surface pattern selected from one or more of i) diamond; ii)raised points; iii) ridges; iv) grooves; v) dimpled; vi) cross hatch;and vi) circular.
 10. The tool of claim 1 further comprising a hydraulicvalve coupled between the diverter valve and the extendable gripperelement for supplying hydraulic pressure to extend the gripper element.11. The tool of claim 1 further comprising a hydraulic drive device forsupplying hydraulic pressure to extend the gripper element.
 12. The toolof claim 11, wherein the hydraulic drive device comprises a motor andpump for pumping drilling fluid at high pressure to extend the gripperelement.
 13. The tool of claim 1, wherein the diverter valve includes apiston and a seal axially moveable by the piston to seal a main mudstream flow path and open an aperture for allowing the mud stream toenter the annulus.
 14. The tool of claim 1 further comprising anexpandable packer coupled to the drill string below the diverter valveto isolate the test device from pressure variations in an annulusbetween the tool and borehole wall while diverter valve is divertingfluid.
 15. The tool of claim 1, wherein the test device comprises: i) anextendable probe adapted to admit formation fluid into the test device;and ii) a sensor for sensing a characteristic of the admitted fluid, thesensed characteristic being used in part to determine the parameter ofinterest.
 16. The tool of claim 1, wherein the drill string portioncomprises a selectable nonrotating sleeve coupled to the drill string.17. The tool of claim 16, wherein the coupling between the nonrotatingsleeve and drill string includes a spring and bearing to allowprogression of the drill bit while the gripper element anchors thenonrotating sleeve.
 18. The tool of claim 1, wherein the extendablegripper element comprises a first extendable gripper element whenextended anchoring a first drill string portion and a second extendablegripper element axially displaced from the first extendable gripperelement, the second extendable gripper element when extended anchoring asecond drill string portion.
 19. The tool of claim 16, wherein the testdevice is adapted to determine the parameter of interest while the drillbit progress through the formation.
 20. The tool of claim 1, wherein thetest device comprises a sensor for sensing a characteristic of theadmitted fluid, the sensed characteristic being used in part todetermine the parameter of interest.
 21. The tool of claim 1, whereinthe sensed characteristic includes one or more of i) temperature; ii)pressure; iii) formation fluid composition; iv) resistivity; v) watercontent; vi) mobility; and vi) nuclear properties.
 22. A system foracquiring a downhole parameter of interest while drilling a boreholethrough a formation, the system comprising: a) a drill string having arotatable bit at a distal end thereof, the tool comprising: b) anextendable gripper element disposed on the drill string, wherein theextendable gripper element forcibly engages the borehole wall to anchorat least a portion of the drill string radially, axially andcircumferentially while the borehole wall is engaged by the extendablegripper element; c) a diverter valve coupled to the drill string todivert drilling fluid into the annulus; d) a test device coupled to thedrill string portion, the test device including a sensor for measuring adesired downhole characteristic and for providing an output signalrepresentative of the measured characteristic; and e) a processorreceiving and processing the output signal, the processed signal beingindicative of the parameter of interest.
 23. The system of 22, whereinthe processor is coupled to the drill string at a downhole location, thesystem further comprising a transmitter for transmitting the processedsignal to a surface location.
 24. The system of 22, wherein theprocessor is located at a surface location the system further comprisinga transmitter for transmitting the output signal to the to the processorfor surface processing.
 25. The system of 22, wherein the processor iscoupled to the drill string at a downhole location, the system furthercomprising a downhole memory device for storing the processed signal.26. The system of claim 25 further comprising a transmitter fortransmitting to a surface location selected values from the storedsignals.
 27. The system of claim 22, wherein the extendable gripperelement includes a pad mounted on the gripper element to increasefrictional force between the borehole wall and the gripper element, thepad having a conical shape pressed into mudcake when the extendablegripper element engages the borehole wall.
 28. The system of claim 22,wherein the extendable gripper element includes a textured pad mountedon the gripper element to increase frictional force between the boreholewall and the gripper element.
 29. The system of claim 28, wherein thetextured pad includes a surface pattern selected from one or more of i)diamond; ii) raised points; iii) ridges; iv) grooves; v) dimpled; vi)cross hatch; and vi) circular.
 30. The system of claim 28, wherein theextendable gripper element further includes one or more pistons operableto extend the pad to engage the borehole wall.
 31. The system of claim28, wherein the pad is a single pad.
 32. The system of claim 28, whereinthe pad is a plurality of pads.
 33. The system of claim 28, wherein thepad is a single elongated pad attached to a housing using at least oneof i) a flexible member coupling the pad to the housing and ii) a membercoupling the pad to the housing at a pivot point.
 34. The system ofclaim 28, wherein the pad has a tapered end.
 35. The system of claim 22further comprising a hydraulic valve coupled between the diverter valveand the extendable gripper for supplying hydraulic pressure to extendthe gripper.
 36. The system of claim 22 further comprising a hydraulicdrive device for supplying hydraulic pressure to extend the gripperelement.
 37. The system of claim 36, wherein the hydraulic drive devicecomprises a motor and pump for pumping drilling fluid at high pressureto extend the gripper element.
 38. The system of claim 22, wherein thediverter valve includes a piston and a seal axially moveable by thepiston to seal a main mud stream flow path and open an aperture forallowing the mud stream to enter the annulus above the gripper element.39. The system of claim 22 further comprising an expandable packercoupled to the drill string below the diverter valve to isolate the testdevice from pressure variations in an annulus between the drill stringand borehole wall while diverter valve is diverting fluid.
 40. Thesystem of claim 22, wherein the test device comprises an extendableprobe adapted to admit formation fluid into the test device, wherein thedesired characteristic sensed by the sensor relates to the admittedfluid.
 41. The system of claim 22, wherein the drill string portioncomprises a selectable nonrotating sleeve coupled to the drill string.42. The system of claim 41, wherein the coupling between the nonrotatingsleeve and drill string includes a spring and bearing to allowprogression of the drill bit while the gripper element anchors thenonrotating sleeve.
 43. The system of claim 22, wherein the extendablegripper element comprises a first extendable gripper element whenextended anchoring a first drill string portion and a second extendablegripper element axially displaced from the first extendable gripperelement, the second extendable gripper element when extended anchoring asecond drill string portion.
 44. The system of claim 41, wherein thetest device is adapted to sense desired characteristic while the drillbit progresses through the formation.
 45. The system of claim 22,wherein the sensed characteristic includes one or more of i)temperature; ii) pressure; iii) formation fluid composition; iv)resistivity; v) water content; vi) mobility; and vii) nuclearproperties.
 46. The system of claim 22, wherein the extendable gripperelement includes a textured pad for engaging the borehole wall.
 47. Thesystem of claim 46, wherein the textured pad includes a surface patternselected from one or more of i) diamond; ii) raised points; iii) ridges;iv) grooves; v) dimpled; viO cross hatch; and vi) circular.
 48. A methodof isolating a downhole test device from noise, comprising: a) conveyinga drill string into a well borehole, the drill string having a rotatablebit at a distal end thereof and an inner bore for conveying drillingfluid from a surface location to the drill bit; b) anchoring a drillstring portion to the borehole wall using an extendable gripper elementsuch that the drill string portion is anchored radially, axially andcircumferentially while the borehole wall is engaged by the extendablegripper element; c) diverting drilling fluid into an annulus surroundingthe drill string portion using a diverter valve; and d) obtaining adesired characteristic using a sensor disposed on the anchored drillstring portion.
 49. The method of claim 49, wherein anchoring the drillstring portion includes engaging the borehole wall with a pad mounted onthe extendable gripper element to increase frictional force between theborehole wall and the gripper element, the pad having a conical shapepressed into a mudcake when the extendable gripper element engages theborehole wall.
 50. The method of claim 48, wherein anchoring the drillstring portion includes engaging the borehole wall with a textured padmounted on the extendable gripper element to increase frictional forcebetween the borehole wall and the gripper element.
 51. The method ofclaim 50, wherein the textured pad surface includes a surface patternselected from one or more of i) diamond; ii) raised points; iii) ridges;iv) grooves; v) dimpled; vi) cross hatch; and vi) circular.
 52. Themethod of claim 50, wherein the extendable gripper element furtherincludes one or more pistons and a pad, the pistons operable to extendthe pad to engage the borehole wall.
 53. The method of claim 50, whereinthe pad is a single pad.
 54. The method of claim 47, wherein the pad isa plurality of pads.
 55. The method of claim 50, wherein the pad is asingle elongated pad attached to a housing using at least one of i) aflexible member coupling the pad to the housing and ii) a membercoupling the pad to the housing at a pivot point.
 56. The method ofclaim 50, wherein the pad has a tapered end.
 57. The method of claim 48further comprising supplying hydraulic pressure to extend the gripperelement using a hydraulic valve coupled between the diverter valve andthe extendable gripper element.
 58. The method of claim 48 furthercomprising supplying hydraulic pressure to extend the gripper elementusing a hydraulic drive device.
 59. The method of claim 58, wherein thehydraulic drive device comprises a motor and pump, the method furthercomprising pumping drilling fluid at high pressure to extend theextendable gripper element.
 60. The method of claim 48, whereindiverting the drilling fluid includes sealing inner bore flow path usinga piston and a seal axially moveable by the piston and opening anaperture for allowing the drilling fluid to enter the annulus.
 61. Themethod of claim 48 further comprising isolating the test device frompressure variations in the annulus between the drill string and boreholewall while the diverter valve is diverting fluid using an expandablepacker coupled to the drill string below the diverter valve.
 62. Themethod of claim 48, wherein the obtaining a desired characteristicincludes extending a fluid admitting probe to engage the formation andwherein the characteristic related to the admitted fluid.
 63. The methodof claim 48, wherein the drill string portion comprises a selectablenonrotating sleeve coupled to the drill string and wherein anchoring thedrill string portion comprises anchoring the nonrotating sleeve.
 64. Themethod of claim 63, wherein the coupling between the nonrotating sleeveand drill string includes a spring and bearing, the method furthercomprising rotating the drill bit to extend the borehole while anchoringthe nonrotating sleeve with the extendable gripper element.
 65. Themethod of claim 48, wherein anchoring the drill string portion furthercomprises anchoring a first drill string portion and a second drillstring portion and wherein the extendable gripper element comprises afirst extendable gripper element when extended anchoring the first drillstring portion and a second extendable gripper element axially displacedfrom the first extendable gripper element, the second extendable gripperelement when extended anchoring the second drill string portion.
 66. Themethod of claim 63, further comprising obtaining the desiredcharacteristic while the drill bit progress through the formation. 67.The method of claim 48, wherein the sensed characteristic includes oneor more of i) temperature; ii) pressure; iii) formation fluidcomposition; iv) resistivity; v) water content; vi) mobility; and vii)nuclear properties.